I'm new here, this is my first attempt at creating a cascading sand-like effect, Its far from perfect but considering it is over a million particles and uses collision I'm fairly happy with it. Just imagine the nightmare of getting this to work with Pflow.

Turned out really good.
You might want to check "upress" scene files in the samples.
There you can see how to make "low res" particle simulation, and then drive much larger amount of particles with it.